1. Technical Field
The present disclosure relates to the management of a rechargeable battery comprising a plurality of cells connected in series and possibly in parallel. The present disclosure applies, for example, but not exclusively to the batteries of electric or hybrid vehicles.
2. Description of the Related Art
An electric vehicle uses only an electric engine powered by a propulsion battery to be propelled. The propulsion battery of an electric vehicle is charged by a source of electrical energy external to the vehicle. A hybrid vehicle comprises both an electric engine and an internal combustion engine to be propelled. The electric engine of a hybrid vehicle is powered by a propulsion battery which is charged by the internal combustion engine. The propulsion battery of some hybrid vehicles may also be charged by a source of electrical energy external to the vehicle.
The propulsion battery of an electric or hybrid vehicle typically comprises several parallel branches of several dozens to several hundreds of cells connected in series. Such a battery has a relatively high cost, which may reach half the price of the vehicle in which it is installed. It is therefore desirable to extend as much as possible the duration of use of such a battery.
A faulty cell may not conduct electrical current any longer. The result is that all the other cells of the same branch, i.e., those connected in series with the faulty cell, are disconnected from the battery circuit. Consequently, the battery looses a capacity corresponding to that of a branch of cells. For example, if the battery comprises four branches of four cells, one faulty cell may cause a loss of capacity of 25% instead of a loss of capacity of 6.25% corresponding to the loss of a single cell. In addition, if a whole branch of cells is faulty, the battery may not be able to supply enough electrical current to power a propulsion engine of vehicle. It is then necessary to replace the battery.